The present invention relates to a transfer case for four wheel drive vehicles and, more particularly, to a power take-off arrangement for a planetary gear reduction assembly supported within the transfer case.
It is a desirable option to provide a power take-off arrangement for a transfer case which is readily accessable and compact. Conventionally, it had been the practice to mount a separate power take-off gear on the input shaft of the transfer case for delivering torque from the input shaft to a power take-off gearbox. However, such arrangements typically require extensive redesign of the existing transfer case including extending the input shaft and transfer case housing to accommodate the power take-off gear. Unfortunately, space limitations generally make such design adjustments impractical or financially prohibitive.
As disclosed in U.S. Pat. No. 4,604,908 issued Aug. 12, 1986 to Dolan and commonly assigned to the present assignee of the instant application, a power take-off arrangement is provided in association with a planetary gear reduction assembly. In general, the power take-off gearbox is driven by the planetary gear assembly at a reduced speed relative to the input shaft. More specifically, the transfer case housing supports an annulus gear and the input shaft which terminates in an axial flange portion defining an integral sun gear. A rotatably carrier assembly supports a plurality of planet gears and includes an inboard carrier ring having peripheral gear teeth adapted to mesh with an input gear of the power take-off gearbox. While the power take-off arrangement disclosed in U.S. Pat. No. 4,604,908 performs satisfactory, by virtue of its construction the loading imposed by the power take-off input gear on the input carrier ring caused eccentric loading to be transferred to the planetary gear reduction assembly. As such, a bending moment is exerted on the planetary gear reduction assembly which may result in excessive gear wear, binding, and/or overstressed conditions during operation of the transfer case in its power take-off mode.